1. Field of the Invention
This invention relates to reciprocatory devices, comprising a movable part which reciprocates relatively to a fixed part and which is associated with means to adjust the outward limit of the reciprocatory movement. The invention is of particular, but by no means exclusive, application to door catches in which case the movable part provides the catch member and the fixed part is the body of the catch which is fitted to the door.
2. Description of the Prior Art
The invention is applicable to roller door catches, which have a reciprocatory plunger part which projects from a door-mounted fixed housing part and carries a roller which engages a recessed keeper mounted on the adjacent door frame pillar. Such a catch has a return spring within the housing which urges the plunger to the outward limit of its reciprocatory movement, which is the normal resting position of the roller at which it engages a striker portion of the keeper on door closure. Adjustment means are commonly provided which provide for adjustment of this position to suit the gap between the edge of the door and the frame pillar, so that the outward projection of the roller can be appropriately set when the catch is fitted. However, with all the catches presently available subsequent adjustment to accommodate changes in said gap either requires that the catch should be removed from the door or else involves an otherwise complicated procedure, for example requiring that a thin screwdriver should be inserted through a diametral bore in the roller.
It has, however, been proposed in U.K. Pat. Nos. Nos. 1,098,721 and 1,180,553 to provide a reciprocatory device in the form of a roller door catch with automatic in-use adjustment of the outward reciprocatory limit so that, for example, day-to-day changes in the door edge gap due to shrinkage or expansion with changing atmospheric conditions are continually accommodated to ensure satisfactory catch operation at all times. This is referred to hereinafter as an "auto-set" facility, and according to such proposals this is achieved by an adjustment member which has clutch engagement with the catch housing and a limited range of reciprocatory movement with the catch plunger, beyond which further plunger movement is accommodated by rotational adjustment movement of that member. The clutch engagement limits the outward return movement of the member and plunger.